Tracking the Chestnut Blight

Chestnut Blight Disease and the Explorations of Frank N. Meyers

• Written by Bill Lord, member TACF
• posted to TACF Growers list on December 20, 2005
• picture from The World's Work Magazine published in 1909

Sleuthing through century old archives reveal scientists as though on a stage. They come to life through a hand-turned roll of brittle microfilm and reprise high moments of chestnut drama.

In 1904 when a few scattered chestnut trees of New York's Bronx Zoological Park were victimized by a new lethal disease, it provoked many questions with no ready answers. What was it, where did it come from, how could it be controlled? W. W. Murrill of the New York Botanical Gardens identified the pathogen as a previously unknown fungus that he named Diaportha [to destroy] parasitica, published in 1906. He also pioneered control measures by removing and burning diseased branches and trees, but concluded that his effort was woefully ineffective. Control, if such were possible, required more knowledge and man power than he was able to mobilize. [7]

The blight was also found in other States, overwhelming a totally inadequate defense. At this time neither the States nor the federal government had the personnel or facilities to cope. As though in shock, they could only advise landowners to harvest their trees before they were killed by the blight. Two pathologists with the Bureau of Plant Industry, U.S. Department of Agriculture, [USDA], Haven Metcalf and Franklin Collins, began field studies in 1908 and in 1911 published Farmers' Bulletin 467, The Control Of The Chestnut Bark Disease. They noted that the blight advanced slowly from the main diseased area and that its rapid spread was due to, "…isolated centers of infection, often many miles in advance of the main line of disease." These coalesced into each other and into the advancing main area. They proposed a control involving the identification and elimination [cut and burn] of the isolated diseased areas combined with the removal of chestnut trees bordering the main line of advance to produce an "immune zone," perhaps 10 to 20 miles wide.

Bulletin 467 noted that although the origin of the blight was unknown, "there is some evidence that it was imported from the Orient with the Japanese chestnut. This view, however, is not held by all investigators."

The Pennsylvania Forestry Department was not particularly interested in where the blight came from. Led by I. C. Williams, they wanted immediate action to save the chestnut, the State's most valuable forest resource. Williams and his supporters persuaded Governor John K.Tenor and the legislature, and in June, 1911, a bill was passed creating, "The Commission for the Investigation and Control of the Chestnut Blight Disease in Pennsylvania." The same year the Commission commenced an ambitious and well financed blight eradication based on methods proposed in Farmers' Bulletin 467.

The Bulletin also stated, "….there is no law whereby the Federal Government can attempt to cope with the emergency." Each State was on it's own but all were encouraged to follow the example being set by Pennsylvania.

Pennsylvania, well into the first year of blight control, was convinced that it was making progress. In February, 1912, Governor Tenor and the Commission hosted a two day convention inviting representatives of chestnut States to participate in a
Region-wide control program

The convention, enlivened by verbal sparring, produced no meeting of the minds. Representatives from States north and east already overrun by the blight followed the lead of W. W. Murrill who argued persuasively that control and eradication was not possible. This included the method proposed by Bulletin 467. When Murrill was asked the fate of the zoological garden's chestnuts, he replied "We are now cutting down the last trees," of the 1,400 chestnuts in the 50 acres comprising the New York Botanical Garden and the Bronx Zoo. [7]

There was also a major discussion on the origin of the blight. Some agreed with George P. Clinton of Connecticut that the blight fungus was normally a harmless saprophyte that had taken advantage of chestnut trees weakened by a sequence of severe droughts and other environmental stresses. Others agreed with Collins and Metcalf that the fungus was of foreign origin.

The Pennsylvania plan of blight control, though well administered, achieved little more than a delaying action. Early hope that blight elimination in advanced areas would be successful were proved false by recurring outbreaks. No work ever commenced on the proposed immune zone. Field activities ceased as of 1913. [7]

Haven Metcalf, however, continued to pursue all leads tracking the blight. He probably first became aware that the Japanese chestnut possessed blight resistance from the work of USDA plant breeder Dr. Walter Van Fleet and his chestnut hybrid planting in northern New Jersey. In 1908 the blight infected his trees and Van Fleet observed, "The hybrids between the chinquapins and native and European chestnuts were quickly infected, but those with Japan varieties appeared far more resistant." [10]

In the fall of 1912, at a time when the sharp debate at the February Convention still weighed on Metcalf's mind, he got some exciting evidence. Material received in Washington, D. C. from a chestnut orchard in Agassiz, British Columbia. was cultured by pathologist C. L Shear in the USDA laboratory and identified as the chestnut blight. According to the Canadian government there were no chestnut trees within 500 miles. The orchard contained trees of, "oriental, European, and American origin." Some of the shipments of incoming nursery stock were known to come from the Orient because they were still wrapped in the, "peculiar mats and casing of those countries." [9]

Metcalf and Shear contacted David Fairchild, the young and initial chief of the USDA's Office of Foreign Seed and Plant Introduction. Fairchild and his staff of plant explorers searched the far corners of the world to collect and send plant material of value and interest to America. Metcalf and Shear probably would have preferred to contact an explorer in Japan but Fairchild had just the man for him, Frank N. Meyer. Meyer had returned to American in April, 1912, following the second of four trips to Asia. Prior to embarking for China by way of Europe in the fall of 1912, he had a busy schedule visiting plant experiment stations, nurseries and agricultural schools. Apparently Metcalf and Shear just missed meeting him. By the time they talked with Fairchild, Meyer was outward bound. Although he had to be aware of the devastating chestnut blight, when he boarded ship neither the chestnut nor the blight were part of his agenda. [2]

Fairchild knew he had the right man. In 1907, during his first trip to China, Meyer found native chestnut growing on the grounds of an old temple north of Peking, [Beijing] and sent packages of nuts to Washington. [2] At this time the Chinese chestnut [C. mollissima] was all but unknown in eastern America. In contrast, the Japanese chestnut {C. crenata] had been grown in America as an orchard and ornamental tree since 1876. [1]

Fairchild communicated Metcalf's request to search for evidence of the blight and Meyer received it when he arrived in Peking in May, 1913. A small specimen of diseased bark was also sent, plus a description of the fungus. By recent agreement among mycologists it was now known as Endothia parasitica. [2]

There is quite a story in the life of Frank N. Meyer. The following tells about this remarkable man and his plant discoveries and introductions. Emphasis is given to his experiences with the chestnut and the chestnut blight.

He was born in Amsterdam, Holland in 1875 and christened Frans Nicolas Meijer. He died, 1918, in China during his forth exploration trip to the Orient.

Meyer, from his youngest days was fascinated with plants and this aptitude was recognized by his less than affluent parents. At age 14 he was sent to work in the Amsterdam Botanical Gardens where he caught the eye of the man in charge, world famous horticulturist, Hugo de Vries. Meyer was not one who responded to arbitrary orders but he would work from dawn to dusk if properly motivated. De Vries, to his credit, saw that Meyer needed to be handled with care but was well worth the effort. With help from his mentor Meyer completed several university courses in botany. He became head gardener in charge of the experimental garden. [5]

But Meyer had dreams of world travel, perhaps inspired by the exotic plants in the Botanical Gardens. He observed and studied these strangers from foreign lands and wanted to see them on their native terrain. At night, walking home from his work, his musings might lead his footsteps into a dusky distance where he would simply sleep in a haystack. [3]

America was his horizon of choice. He arrived in 1901 and found work in Washington D. C. with the USDA. He wrote letters home full of praise for this land of unequalled opportunity. But staying put and making his fortune held no appeal. His call was to travel and explore; to find plants that would benefit mankind and earn his due of praise and recognition. The following year he entrained for southern California. The sight of swaying palm trees amid an amazing abundance of food crops gave gratifying proof of the bounty that plants could provide. "Here a boy can eat as many walnuts, peaches, figs or watermelons as he wants. The fruit rots on the trees so plentiful is the supply." Within a few months his elation drifted into boredom. His skill as a gardener enabled him to make a good living but once he saved enough money, he was off to a new horizon. From southern California he wandered north where the lovely mountain valley by the sea of Montecito lured him for a brief pause and then, in 1904, he was off by boat for Mexico. He landed at the Pacific port of San Blas and journeyed cross country to the Gulf of Mexico at Vera Cruz. He traveled several hundred miles of the distance on foot. In the remoter areas he slept out doors or in native huts and dined as the natives dined. During his time in Mexico he mailed eight varieties of seeds, including an apricot and a yellow chili pepper, each carefully described, to the USDA Plant Introduction Center in Chico, California. [2]

His work impressed David Fairchild. Mexico, in the remote regions visited by plant explorers, was plagued with banditry. Meyer was not only a dedicated plant explorer but also resolutely brave. What ever the odds, he would complete his mission.

Would he become a plant explorer for the USDA commencing with a trip to China? We can only imagine Meyer's joyful acceptance. The two men became life long friends.

Meyer would make four explorations into the remotest regions of Asia, often as strange and unknown to the natives as the first Europeans were to the Native American. Where possible he covered long distances by train, but thousands of miles were on foot. He hired guides and interpreters and assembled a small caravan of two wheeled carts drawn by whatever beast of burden was available, donkey, mule, horse or ox. Where carts could not go he hired pack animals and coolies. He crossed glaciers and deserts and swamps. He bested thugs and faced down bandits. He went in search of new plants, "of value to mankind," and his quest was like that of a Coronado after gold. When guides and drivers deserted out of fear, he hired new men. His biggest deterrent was the many dialects, sometimes changing from village to village. Without an interpreter he could not navigate or communicate. In such places his fluency in English, French, Dutch, German and Russian was all Greek to the natives. He shared the lot of the land, at times sleeping side by side with other travelers on brick beds in village inns infested with lice; eating unsanitary food, and plodding though winter blizzard, or summer down pour. He battled though recurrent attacks of malarial fever and dysentery. He parlayed and parried with government officials over authorization and permits and, "was he really a plant explorer or a spy?" He traveled through countries where the American dollar had no value and he dealt in coins of silver, copper and brass, carried in sacks slung over a donkey's back. [2]

He looked forward to reaching a town or city with an international post office. There he would spend the entire night avidly reading his accumulated mail. He particularly enjoyed letters from Fairchild, telling him of new requests for specific plants, and best of all, telling him that some of his plant introductions were receiving high praise.
Meyer's prose was too highly laced with botanical names to be of general interest but he had a poet's touch. In speaking of Iris Kaempferi, "There are dreams of beauty among them," and describing a burned forest in Siberia's Altai mountains, "…here and there a naked limb pointing to the blue and sliver sky as if imploring pity." [2]

When a post office had dependable communications Meyer would mail packages of plant materials; seeds, cuttings, and scions. Seeds were placed in charcoal or paraffin; cuttings and scions in carefully dampened peat moss; neither too moist nor too dry. Most were sent to Chico, to Washington, or to the Arnold Arboretum of Harvard University. One of his primary incentives was to acquire reproductive material of useful plants that could survive harsh growing conditions and his success in this endeavor lives with us today. His Siberian elm [Ulmus pumila], "…now thrives from Canada to Texas breaking the searing winds on vast prairies." The wild Chinese pears, [Pyrus ussuriensis and P. calleryana] provide root stocks resistant to the fire blight [Bacillus amylovarus]. China's northern wild peach, [Prunus davidiana] provides root stock for peach, apricots and plums that can thrive in the dry soil of northern states. [2]

Of interest is his communication with W. W. Murrill. In 1910 he sent him, "a strange algae and a red fungus," from the Crimea; and "two valuable fungi," from China in 1917. [2]

Meyer made four explorations:

[1] 1905-1908 crossing the Pacific and radiating northeast from the Beijing area across Korea and into Manchuria and southern Siberia, and southeast into central and coastal China.

[2] 1909-1912 crossing the Atlantic and through Europe to Moscow and the Crimea; then over the southern expanse of Tsarist Russia and Siberia to the western border of China; returning across northern Siberia to Moscow, and home via the Atlantic.

[3] 1912-1915 Crossing the Atlantic and reaching China by way of Russia and Siberia. With Peking as his main base he explored central China and home via the Pacific

[4] 1916-1918 Arriving in Peking by way of the Pacific and concentrating his effort in the province of Hupeh [now Hubei] in central China.

Meyer embraced the chestnut and the blight as a major project when he received Fairchild's letter upon his arrival in Peking in May, 1913. As previously mentioned he identified native chestnut on the grounds of the Fa Ha Ssu Temple near Peking in the fall of 1907. During his second trip he did not mention the chestnut at all, but he may have seen some while in the Caucasus Mountains of Georgia..

The importance of Fairchild's letter required prompt attention and Meyer left directly for chestnut country north and east of Peking. He had a description of the blight and a sample of diseased bark, and he must have studied them thoroughly. His letter of discovery, June 3, 1913, is a careful history that also exudes with the joy of discovery.

":Here I am sitting in a Chinese inn in an old dilapidated town to the northeast of Peking, between tsun hua tcho and Yehol and have been busy for several days collecting specimen of this bad chestnut bark disease and taking photos of same. It seems that the Chinese fungus is apparently the same as the one that kills off the chestnut trees in north eastern America. I hope to send a cablegram through the American Legation in Peking about this discovery, to the Secretary of Agriculture. I am also enclosing a small piece of bark with this fungus on it. More material I hope to send off from Tienstein [Tianjin] and Peking. Here are my observations. This blight does not, by far, do as much damage to Chinese chestnut trees as to the American ones. Not a single tree could be found which had been killed entirely by this disease, although there might have been such trees, which had been removed by the ever active and economic Chinese farmers.

"Dead limbs, however, were often seen and many a saw wound showed where limbs had been removed. Young trees and trees on level, poor soil were much more attacked than old trees or trees growing on richer, sloping soil at the base of rocks and hills. The disease is apparently losing its virulence and the wounds on the bigger majority of the trees were in process of healing over. The Chinese ascribe this disease to the workings of caterpillars, grubs and ants, which are very freely found beneath the bark on these diseased spots and the main trunk and branches.

"To combat the disease they scrape the bark clean every winter or early spring. The strips of bark are all collected, tied up in bundles and sold as fuel.

"This Chinese chestnut does not grow to such size as the American one. Trees over 40 feet are rare. They are of low branching habits with open heads, more or less the way of European chestnut, Castanea vesca [C. sativa]. The lumber is hard, but even a good sized tree produces relatively little good lumber."

In Meyer's comparison of the Chinese chestnut's growth pattern to that of the European chestnut, he may have been referring to the 'Marrone', an orchard tree common in France and Italy. As described by Dr. Sandra Anagnostakis of the Connecticut Experiment Station, "'Marrone'….are probably European X Asian hybrids….They were selected by Monks in what is now Turkey in the 1100's. 'Marrone' are usually apple like orchard trees, grafted on European root stocks and their nuts are large. Trees of the pure species are tall and straight like American chestnuts….Nuts of the pure species are about the size of American chestnuts." [1] Meyer continues.

"Old wounds are to be observed here and there on ancient trees showing that 40 or 50 years ago similar outbreaks of fungus disease have taken place. The maximum age of these Chinese chestnuts seen in its native habitat seems to be between 250 and 300 years, but when that old they are already in decay. The tree is not a fast grower and does not begin to bear until 12-15 years old. The soil best suited to these is a warm, well decomposed granite, with perfect drainage, in which locality they love the lower slopes of hills and mountains where they will be sheltered.

"The valleys and ravines in the lower altitudes of the Rocky Mountain regions would probably supply congenial localities for these chestnuts.

"This northern Chinese chestnut is not a lumber tree but attempts might be made to cross it with the American species trying to give the last one more hardiness against disease.

"The nuts of this Chinese chestnut are not as large as those from the European or Japanese forms, but they are very sweet and are in great demand in China.

"What is the remedy used in America against the blight? What I see of it I would suggest spraying of the trunks and branches in spring time before the leaves come out, with an emulsion of an oily substance, like diluted tar, diluted crude petroleum, diluted whale oil with lime, etc., anything that would cover up these fungi with something sticky and biting, that would prevent them from spreading their spores and would greatly lessen the chance of healthy trees catching this fungus by making their bark not a good receiving place for spores floating in the air. Of course this only applies to districts where the blight is just starting or where it has not made its appearance as yet.

"In places where it is very serious I suppose the only thing is to cut down all trees which are attacked and to make a chestnut free belt between the affected region and the non affected one. [This is an integral part of the control method advocated by Metcalf. The Pennsylvania Blight Commission was denied putting it into effect by the overwhelming advance of the blight.] I am, of course, not an expert at this problem and I simply offer these suggestions as they come into my head while thinking about possible means for checking this terrible blight.

"The great chestnut district of North China lies in the mountain valleys between the town of San tuning and the great Chinese wall, 4 to 5 days journey by carts from Peking to the northeast and one and one half to two days journey by carts from the railroad station, Tang shan, on the railroad from Tienstin to Shan hai kwan. Most of the trees seem to be of original growth, but also plantations have been made at the foot of the mountain and hills."

Throughout his many years in China Meyer refers to cities and towns that are not found on present day maps. Such is the case with Tang shan and Shan hai kwan. The fact that the majority of the place names have changed from Meyer's time to the present makes geographical location an often perplexing adventure. It is usually possible to determine the present identity of the provinces and larger cities but not the identity of the many small towns noted by Meyer. Fortunately the "San tuning" mentioned by Meyer is listed in the 15th edition, 1993 Encyclopedia Britannica atlas as Santunying, 100 miles eastward from Beijing and ten miles south of the Great Wall as it nears its eastern terminus at an arm of the Yellow Sea. According to my atlas the "great chestnut district," described by Meyer, "…is about 10 miles wide between Santunying and the Great Wall, and widens as it extends westward to the north of Beijing.

"And now I have a few questions to do, which I hope you or somebody else may see fit to answer. Who is the man who first thought this chestnut bark fungus might occur in China and what were his reasons for thinking so?"

This indicates that Meyer was not aware of Metcalf's conviction of the blight's Asian origin.

"Where was the fungus first found? On Long Island, isn't it? Could it have been brought over in shipments of Japanese plants? If so, this same disease might occur in Japan. Have you written to someone living near a chestnut district in Japan?

"You say in your letter of Feb 26 that if I discover the same species in China, it will affect the whole chestnut blight situation in America. Please state in what way?" [6]

David Fairchild might have paraphrased the words of a then much quoted poet, "How much does this mean to us? Let me count the ways." The men at USDA were victors in the debate on the origin of the blight. They also had high hopes that the apparently very strong blight resistance of the Chinese chestnut could be transmitted to the American chestnut. The sweet tasting nut would be a boon to orchardists.

Shear and other USDA scientists made careful comparison tests between the "American" and the "Chinese" fungus. They found that the spores from each source grew identical colonies of mycelium when cultured in the same media. When mycelium from either source was inoculated into American chestnut trees, the same type canker developed. Bark peeled away from a canker revealed the tell tale mycelial "fans" at the leading edge of the expanding lesion.

The blight fungus produces two types of spores, asexual conidia spores and sexually produced ascospores. The production of ascospores from the inoculations was the last proof required and these were finally collected from infected trees in a carefully conducted procedure in February, 1915. [9]

Through 1914 and most of 1915, Meyer traveled southwest and southeast through China, now very alert for the Chinese chestnut and the blight. He collected blight specimens from native trees, March 21 in Shangtung [Shandong] province by the Yellow sea, and from Shensi [Shanxi] province to the west, September 21, 1914. The following year, June 26, 1915, he collected blight specimens in Chekian [Zjhejiang] province inland from the East China Sea. Writing from Chekian, Meyer remarked, "Well, I have a few interesting discoveries to report. First, there are many specimens of Castanea mollissima scattered at the bases and on the lower slopes of the hills around here, and these chestnuts are seriously attacked by the bark fungus and in my estimation are going to succumb to it these coming years." This was sobering news to the men at USDA. The Chinese chestnut varied in its blight resistance. [2]

At Fairchild's request, Meyer went to Japan and was again successful in collecting what proved to be Endothia parasitica from a Japanese chestnut tree in mountains approximately 100 miles north of Tokyo, September 17, 1915. [9]

Meyer's time in Japan was brief but productive. He found the blight to be quite prevalent, but surprisingly, it was not recognized as such. Two of his Japanese associates wished to see the evidence and Meyer located some infected trees near Tokyo. [9]

Meyer returned to an enthusiastic welcome from Fairchild in Seattle, October, 1915. To Meyer's surprise and delight Fairchild had journeyed across the continent from Washington and was there to greet him at the pier. Meyer stood at the rail shouting his exultant conviction that the blight had come to America by way of Japan. Then he was deluged with immigration officers and newsmen. The good friends finally got together and, "…spent half the night talking." [2]

Meyer and Fairchild visited the Chico Plant Introduction Garden in California where many of his introductions were now flourishing, some doing better than in their native land; dwarf, sweet tasting lemons, drought resisting almonds, and some of the Chinese chestnut hybrids developed by Dr. Van Fleet. Then he left on a triumphant tour of nurseries and experiment stations across America. But his élan was jolted by the depressing news that a large shipment, "representing almost eighteen months hard work," had been destroyed by a hurricane during a layover in Galveston. "This loss left a wound that never healed. [2]

By mid 1916 Meyer was bound again to Asia to explore previously unvisited central China. The chestnut was now a prominent part of a very demanding agenda. America was headed for war giving Meyer's exploration and collecting an added urgency; for seed and scions of blight resistant native pear, for drought resistant davidiana peach, for walnut, tung nut and for every species of native chestnut, and on and on and on. Incoming mail brought added requests ; for, "….any irises possible and particularly Iris speculatrix." A Mr. Norton would like to secure a number of varieties of Chinese asparagus. A younger Meyer had remarked, "Work is to me what medicine is for sick people." [3] But Hupeh province in central China would test his stamina and resolve. "If I had seven bodies I could use all in my work." Most of his travel was on foot accompanied by his interpreter, guide and two wheeled carts to transport his collections. Malaria and dysentery were endemic and the country was immersed in constant warfare. [2]

"The more I travel around in [western] Hupeh, the more I am impressed with its immenseness, nothing but mountains and valleys and hills and dales. Put the State of Montana across Georgia and neighboring States and you have some idea of topography and climate of Hupeh. No one man can ever cover this whole province on foot and really one cannot travel otherwise; there are no real roads, nothing but trails and accommodation and food supplies of the poorest imaginable. As I am writing we hear the rickety noise of rifle fire, for the Northern and Southern troops are at battle only a mile or so north of the city. That we do not live "at ease," you can easily imagine."
Letter to Mr. Fairchild, Feb 1, 1918, from Ichang [Yichang]. Hupeh. [8]

He found the Chinese chestnut, C. mollissima, and also the dwarf chestnut, C. seguinii, growing on the mountain slopes and hills of central and western Hupeh. Over time he was able to ship scions and several hundred pounds of Chinese nuts and a lesser amount of dwarf. All plant material was carefully prepared and transported in sturdy crates, but the time and layovers required to make the journey down the Yangzte River several hundred miles to Shanghai and then across the Pacific handicapped his effort. On average about half the nuts germinated and one valuable shipment was almost totally ruined. Fortunately a few of the nuts had sprouted and, "these we shall save." [8]

Meyer's correspondence mentions that he was also searching for a species of native chinquapin, Castanea vilmoriniana [C. henrii], a tree reputed to attain a height of 90 feet, but I found no evidence of any collecting. [8]

He found an abundant presence of the blight. "I noticed plenty of Endothia parasitica in cultivated as well as in wild Castanea mollissima right from Ichang to beyond Hsing shan hsian. On some places it was very serious especially one day's journey N. W. of Hsing shan hsien in wild trees. Please communicate this to Dr. Shear. I got some wild chestnut tho' for which please see No. 2458a and 2459a." [8]

Warfare abated in the spring and Meyer was finally able to move his crated plant collection by river boat and travel down the Yanzte en route to Sanghai on the coast. He intended to ship his collection to America and remain in China, "to collect several hundred pounds of chestnuts and a quantity of seeds of the northern form of the wild pear near Peking." On the final leg of his journey on the night of June 1, 1918 he disappeared from aboard the steamer Feng Yang Maru. His body was found ashore a few days later and he was buried in Shanghai. The cause of death was never determined but his health had seriously deteriorated. He may have fallen or jumped into the dark waters of the Yangzte. [2]

Meyer drove himself, sometimes to the point of collapse to collect and transport plants that would make life better for the citizens of his adopted land. We live better because of what he lived and died for.

References

1. Anagnostakis, S. L., P. Gordon, and F. V. Hebard. 1998. Identification of Chestnut Trees. Annual Report of the Northern Nut Growers Association 89:1-4.
2. Cunningham, I. S., 1984. Frank N. Meyer, Plant Hunter in Asia. Iowa State University Press, Ames, Iowa
3. Derksen, L., 1957. The Restless Frank N. Meyer. Published in Panorama, Vol. 44, no. 20, National Agricultural Library, Special Collections, Beltsville, Mld.
4. Metcalf, H. and J. F. Collins. 1911. The Control of the Chestnut Bark Disease. USDA Farmers' Bltn. 467
5. Meyer, Frank N. 2003. Papers of Frank N Meyer, 1907-1914, Arnold Arboretum Archives, Harvard University, Cambridge MA. [internet]
6. National Archives and Records Service [Washington, D. C.] Record Group 54: Records of the Bureau of Plant Industry, Division of Plant Exploration, Vol. 77: Northwestern China Exploration, 1912-1915. [On microfilm, rolls 22, 28, 29, 30]
7. Pennsylvania Chestnut Tree Blight Commission, Final Report, 1914
8. Selections from the correspondence involving Frank N. Meyer's trip to central China, 1916-18, National Agricultural Library, Special Collections, Beltsville, Mld.
9. Shear, C. L., N. E. Stevens, and R. J. Tiller. 1917. Endothia Parasitica and Related Species. USDA Bltn No. 380
10. Van Fleet, W. 1914. Chestnut Breeding Experiences. The Jrnl of Heredity, Vol. 5, pp 19-25